British authorities on Monday released the names of two of the three men who killed seven and injured dozens over the weekend.

Police and the M15 domestic security agency also acknowledged Monday that they had been aware of one of the three alleged London Bridge attackers, Khuram Shazad Butt, 27, a British citizen born in Pakistan, but they had no specific intelligence to indicate he was plotting a terrorist assault.

Butt, 27, was a British citizen who was born in Pakistan, police said. Redouane, 30, had claimed to be Moroccan and Libyan. He also used the name Rachid Elkhdar, with a different date of birth. Inquiries are ongoing to confirm the identity of their accomplice, police said.

The Islamic State, or ISIS, said it was responsible for the vehicle and knife assault, but that claim has not been substantiated. Other attacks have been committed without direct ISIS involvement by terrorists who are sympathizers of the radical group.

NBC News reported Monday that an American bystander was shot in the head by a stray bullet fired by police toward the attackers during the incident on London Bridge and in nearby Borough Market on Saturday night. He is expected to survive.

More people were detained in east London early Monday in connection with the attack. Counterterrorism police raided two addresses in the Newham and Barking areas. “A number of people have been detained and are at present being spoken to,” the Metropolitan Police said in a statement.

Prime Minister Theresa May said the country must do “more, much more” to fight the "evil ideology” of Islamist extremism. She said Britain will review its counterterrorism strategy.

Fabio Lamas, 20, who works at a pub in Borough Market, told NBC he saw the three attackers wearing body armor and brandishing knives before the police arrived.

"I got people to start evacuating inside from our little garden that we have ... and got people to come into the bar and to go into toilets, hide under tables and hide in our cellar where we keep all our stock," he said. "Then I heard shooting and I saw an American guy get shot in the head."

The U.S. Embassy and the Metropolitan Police didn't immediately confirm the report.

The raids came the day after police arrested 12 people in Barking in connection with the rampage. May said Monday that 11 remained in custody and one was released without charge.

May said she thought London Mayor Sadiq Khan was doing "a great job." It followed President Trump deriding and misrepresenting Khan's attempt to calm Londoners after the attack.

“At least 7 dead and 48 wounded in terror attack and Mayor of London says there is "no reason to be alarmed!" Trump tweeted Sunday. Khan had told Londoners there was no “reason to be alarmed” by an increased police presence, and said of the terrorists, “we will never let them win.”

Trump maintained the feud with Khan on Monday, tweeting: "Pathetic excuse by London Mayor Sadiq Khan who had to think fast on his 'no reason to be alarmed' statement. MSM is working hard to sell it!"

Pathetic excuse by London Mayor Sadiq Khan who had to think fast on his "no reason to be alarmed" statement. MSM is working hard to sell it!

The attackers rammed pedestrians with a van before launching frenzied stabbings in the market. The three assailants were shot dead by police. The Islamic State claimed responsibility for the attack.

Metropolitan Police Commissioner Cressida Dick told the BBC that police seized a "huge amount" of forensic material and evidence from the van and in the raids.

Twenty-one of the 48 people injured in the attack remained in critical condition late Sunday.

The first victim to be named was Christine Archibald, 30, who worked in a homeless shelter before moving from Canada to Europe to be with her fiancé.

"We grieve the loss of our beautiful, loving daughter and sister. She had room in her heart for everyone and believed strongly that every person was to be valued and respected," said her family, who live in Castlegar in British Columbia, in a statement.

People attend a vigil at Potters Fields Park in London on June 5, 2017 to commemorate the victims of the terror attack on London Bridge and at Borough Market that killed seven people on June 3.
London police made a fresh round of arrests Monday after the country's third terror attack in less than three months as Prime Minister Theresa May came under mounting pressure over security three days ahead of elections. The aftermath of Saturday night's rampage, which left seven dead and dozens wounded, dominated the campaign trail.
/ AFP PHOTO / Odd ANDERSEN (Photo credit should read ODD ANDERSEN/AFP/Getty Images)
(Photo: ODD ANDERSEN)

French Foreign Minister Jean-Yves Le Drian said a French citizen was also killed.

The attack came days before a general election Thursday. Campaigning resumed Monday after being suspended by major political parties in the aftermath of the attack. London Bridge train station also reopened.

The attack was the third deadly terrorism incident in Britain in less than three months.

In a speech in Downing Street on Sunday, May called for tougher measures to contain Islamic extremism, saying the assaults are not directly linked, but “terrorism breeds terrorism.”

"It is time to say enough is enough," she said.

Harun Khan, the secretary general of the Muslim Council of Britain, agreed with May that things must change.

"We are ready to have those difficult conversations, as equal citizens with an equal stake in this fight," he said in a statement Monday.

"I am pleased that the Prime Minister is speaking about conversation: it implies that we must listen to one another and work together to be part of a truly United Kingdom."

On March 22, five people were killed in London after Khalid Masood rammed his car into pedestrians on Westminster Bridge before fatally stabbing a policeman outside Parliament. Masood was shot dead by police.

On May 22, Salman Abedi, a British-born suicide bomber, killed 22 people and injured scores of others at an Ariana Grande concert in Manchester in northwestern England. Abedi died at the scene.

Grande held a concert in Manchester on Sunday night to aid the victims and their families, drawing tens of thousands of people amid heavy security.

A vigil will be held in central London on Monday evening to remember the victims of the attack.